Fire retardants

ABSTRACT

Fire retardant adducts of 1,4-dihydronaphthalene and halocyclopentadienes and polymer compositions containing said adducts.

This invention relates to adducts of 1,4-dihydronaphthalene andhalocyclopentadienes and fire retardant composition comprisingpolyolefins and adducts of 1,4-dihydronaphthalene andhalocyclopentadienes.

There has been considerable interest in the development offire-retardant compositions, particularly polyolefin compositions havingimproved fire-retardancy.

The general object of this invention is to provide a new class ofcompounds suitable for use as fire-retardants. Another object of thisinvention is to provide polyolefin compositions having improvedfire-retardancy. Other objects appear hereinafter.

I have now found that adducts of 1,4-dihydronaphthalene andhalocyclopentadienes and modifications of said adducts constitute a newclass of fire-retardants, which are compatible with polyolefins andimprove the fire-retardancy of these compositions. Compounds capable ofimproving the fire-retardancy of polyolefins include1,2,3,4-tetrahalonaphthobornadienes, such as1,2,3,4-tetrachloronaphthobornadiene,1,2,3,4-tetrabromonaphthobornadiene;1,2,3,4,7,7-hexahalonaphthobornadienes; 1,2,3,4-tetrachloro-7,7-dialkoxy(methoxy, ethoxy, propoxy)-naphthobornadienes;1,2,3,4-tetrahalo-7-one-naphthobornadienes, etc.2,3,4-trichloro-9,10,42, 9a-tetrahydroanthracene-1-carboxylic acid, etc.

Briefly, most of these compounds can be produced by reacting1,4-dihydronaphthalene and a suitable halo-substituted cyclopentadiene.While all of these adducts can be used directly in polyolefincompositions or converted to other compounds, the 7,7-dialkoxy compoundscan be converted to 7- ones which in turn can be converted totetrahydroanthracene-1 carboxylic acids as explained below.

In somewhat greater detail, 1,4-dihydronaphthalene and a suitablehalosubstituted cyclopentadiene, such as a hexahalocyclopentadiene(hexachlorocyclopentadiene, hexabromocyclopentadiene, etc.).,5,5-dialkoxy-1,2,3,4-tetrachlorocyclopentadiene(5,5-dimethoxy-1,2,3,4-tetrabromopentadiene,5,5-diisopropoxy-1,2,3,4-tetrachloropentadiene, etc.)1,2,3,4-tetrahalocyclopentadiene, (1,2,3,4-tetrabromocyclopentadiene)etc. is heated to a temperature of 100° to 150° C. to form a Diels-Alderadduct. The reaction can be carried out in a solvent, such astetrachloroethylene or without a solvent under atmospheric conditions orin an autoclave under pressure, such as autogeneous pressure.

The 7,7-dialkoxy groups can be converted to keto groups (7-ones) bytreating the adducts with a dehydrating acid, such as sulfuric acid at30° to 40° C., preferably under ambient conditions. The reaction can becarried out in a halohydrocarbon solvent, such as methylene dichloride,1,1,1-trichloroethane, etc.

The 1,2,3,4-tetrahalo-7-one-naphthobornadienes can be converted to2,3,4-trihalo-9,10,4a, 9a-tetrahydroanthracene-1-carboxylic acids byreacting the 1,2,3,4-tetrahalo-7-one-naphthobornadienes with asuspension of powdered alkali metal hydroxide, such as powdered sodiumhydroxide or potassium hydroxide in an aprotic solvent, such astetrahydrofuran, at 0° to 5° C.

All of the aforesaid halo compounds can be added to polyolefincompositions in a concentration of about 5 to 50 parts by weight per 100parts by weight polyolefin to improve the fire-retardant properties ofthe polyolefin composition. For the purpose of this invention the term"polyolefin" includes solid polymers which contain a major proportion(i.e., greater than 50% and generally greater than 75%) of an aliphaticolefin, having from 2 to 8 carbon atoms, such as polyethylene,substantially crystalline polypropylene, propylene-ethylene block orrandom copolymers, ethylene-butene-1 block or random copolymers,polybutene-1, poly(4-methylpentene-1), poly(3-methyl-butene-1), and thelike. The term polyolefin as used herein is, furthermore, intended toinclude copolymers of hydrocarbon monomers with copolymerizable polarmonomers with such functional monomers constituting a minor proportionof the copolymer. Preferred polyolefins are polypropylene andpropylene-ethylene copolymers such as propylene-ethylene terminal blockand multi-segment copolymers. Propylene-ethylene multisegment copolymersare described in U.S. Pat. Nos. 3,296,338 and 3,442,978.

The polyolefin composition can be compounded with various inoccuousadditives, such as inert fillers (fiber glass, zinc oxide, etc.) orother fire retardant agents such as phosphorous compounds (triphenylphosphite), filler (antimony trioxide), etc. The fire retardants lowerthe level of the new additive of this invention necessary to impart aparticular level of fire retardancy.

Although all the adducts of this invention can be used in fire retardantpolyolefin composition, various compounds have additional uses. Forexample, 2,3,4-trichloro-9,10,4a,9a-tetrahydroanthracene-1-carboxylicacid shows severe necrosis to pigweed and moderate retardation againstyellow foxtail weed while 1,2,3,4-tetrachloro-7-one-naphthobornadieneshows 51% control of late blight of tomatoes with no damage to theplants, 80% control of powdery mildew of cucumber with no damage to theplants and 72% control of bacterial leaf spot of tomatoes.

The following examples are merely illustrative.

EXAMPLE I

Thirteen grams 1,4-dihydronaphthalene (0.1 mole) and 27.3 gramshexachlorocyclopentadiene (0.1 mole) were heated at 130° to 140° C. for48 hours in a 100 ml 3-necked round bottomed flask equipped with acondenser, thermometer, heating mantle and magnetic stirrer. The darkreddish-brown liquid solidified on cooling yielding 38.2 grams (94.7%yield) of 1,2,3,4,7,7-hexachloronaphthobornadiene. White coulombiccrystals melting at 139°-140° C. were obtained after recrystallizationfrom methanol. The nmr and ir were consistent with the indicatedstructure and the chemical analysis for1,2,3,4,7,7-hexachloronaphthobornadiene was as follows:

    ______________________________________                                                     Theory     Actual                                                ______________________________________                                        Carbon         44.31        44.75                                             Hydrogen       2.50         2.46                                              Chlorine       52.79        52.90                                             ______________________________________                                    

The corresponding (a) 1,2,3,4,7,7-hexabromonaphthobornadiene, (b)1,2,3,4-tetrachloronaphthobornadiene and (c)1,2,3,4-tetrabromonaphthobornadiene can be obtained by replacing thehexachloropentadiene with an equal molar concentration of (a)hexabromopentadiene, (b) tetrachloropentadiene or (c)tetrabromopentadiene.

EXAMPLE II

One hundred thirty grams 1,4-dihydronaphthalene (1 mole) and 264 grams1,1-dimethoxy-2,3,4,5-tetrachlorocyclopentadiene (1 mole) were heated at140 to 145° C. for 48 hours in a 500 ml 3-necked flask equipped with acondenser, thermometer, heating mantle and magnetic stirrer. The hotliquid was poured into excess methanol yielding 290.77 grams (75.5%yield) of white solid1,2,3,4-tetrachloro-7,7-dimethoxynaphthobornadiene. White coulombiccrystals melting at 106° to 107° C. were obtained afterrecrystallization from methanol. The nmr, ir and chemical analysis wereall consistent with the structure for1,2,3,4-tetrachloro-7,7-dimethoxynaphthobornadiene.

The corresponding (a) 1,2,3,4-tetrabromo-7,7-dimethoxynaphthobornadiene,(b) 1,2,3,4-tetrachloro-7,7-diisopropoxynaphthobornadiene can beobtained by replacing the1,1-dimethoxy-2,3,4,5-tetrachlorocyclopentadiene with an equal molarconcentration of (a) 1,1-dimethoxy-2,3,4,5-tetrabromocyclopentadiene or(b) 1,1-diisopropoxy-2,3,4,5-tetrachlorocyclopentadiene.

EXAMPLE III

Fifty-eight grams 1,2,3,4-tetrachloro-7,7-dimethoxynaphthobornadiene(0.147 mole), 2,000 ml methylene dichloride and 1,250 ml concentratedsulfuric acid were stirred for three hours at room temperature in a 5liter round bottomed flask during which time the reactants changed froma clear fluid to a viscous golden color. The methylene dichloride layerwas separated and the acid layer extracted three times with 300 mlportions of methylene dichloride. The methylene dichloride portions werecombined, washed with water, dried under anhydrous sodium sulfate,filtered and the solvent distilled off yielding 44.4 grams (87% yield)of tan-white 1,2,3,4-tetrachloro-7-one-naphthobornadiene. Clearcoulombic crystals melting at 188°-189° C. were obtained afterrecrystallization from carbon tetrachloride. The nmr and ir wereconsistent with the structure for1,2,3,4-tetrachloro-7-one-naphthobornadiene.

The corresponding 1,2,3,4-tetrabromo-7-one-naphthobornadiene can beobtained by replacing 1,2,3,4-tetrachloro-7,7-dimethoxynaphthobornadienewith an equal molar concentration of1,2,3,4-tetrabromo-7,7-dimethoxynaphthobornadiene.

EXAMPLE IV

Eight and nine-tenths grams 1,2,3,4-tetrachloro-7-one-naphthobornadiene(0.0256 mole) and 100 ml tetrahydrofuran were stirred at 0° C. in a 100ml round necked flask equipped with a drying tube and a magneticstirrer. After 8.25 grams of powdered sodium hydroxide was added, thereactants were stirred at 0° C. for 5 hours. Twenty ml 3.7 Nhydrochloric acid was added to the reactants while maintaining at 0° C.followed by 25 ml water. The tetrahydrofuran was then removed using arotar-evaporator. The residue was dissolved in 100 ml ethyl ether,washed with water, 100 ml 5% by weight aqueous sodium bicarbonate addedfollowed by 15 ml 3.7 N hydrochloric acid forming a precipitate. Theprecipitate was dissolved in ethyl ether, washed with saturated aqueoussodium chloride and dried under anhydrous sodium sulfate. The ethylether was removed with a vacuum yielding 5.1 grams (60% yield) of2,3,4-trichloro-9,10,4a,9a-tetrahydroanthracene-1-carboxylic acid. Whiteneedle-like crystals melting at 209°-212° C. were obtained afterrecrystallization from ethylene dichloride. The nmr, ir and chemicalanalysis were consistent with the structure for2,3,4-trichloro-9,10,4a,9a-tetrahydroanthracene-1-carboxylic acid.

The corresponding2,3,4-tribromo-9,10,4a,9a-tetrahydroanthracene-1-carboxylic acid can beobtained by replacing 1,2,3,4-tetrachloro-7-one-naphthobornadiene withan equal molar concentration of1,2,3,4-tetrabromo-7-one-naphthobornadiene.

EXAMPLE V

One hundred parts by weight crystalline polypropylene having a molecularweight of at least 2,000,000 was blended with 10 parts by weightantimony oxide and either 10 or 25 parts by weight of fire retardantcompound of this invention, pelleted on an extruder having a dietemperature of 425° F. and molded at 380° F. into bars 10 mm long, 3 mmthick and 6 1/2 mm wide. The fire retardancy of the samples wasevaluated according to ASTM D-2863-70. The results are set forth belowin Table I.

                  Table I                                                         ______________________________________                                                                        Oxygen                                        Compound Evaluated  Parts by Weight                                                                           Index                                         ______________________________________                                        Pure Polypropylene              18.5                                          1,2,3,4,7,7-hexachloronaphtho-                                                bornadiene          10          22.1                                          1,2,3,4,7,7-hexachloronaphtho-                                                bornadiene          25          24.3                                          1,2,3,4-tetrachloro-7,7-dimethoxy-                                            naphthobornadiene   10          20.9                                          1,2,3,4-tetrachloro-7,7-dimethoxy-                                            naphthobornadiene   25          22.9                                          1,2,3,4-tetrachloro-7-one-naphtho-                                            bornadiene          10          21.1                                          1,2,3,4-tetrachloro-7-one-naphtho-                                            bornadiene          25          22.9                                          ______________________________________                                    

I claim:
 1. A polyolefin composition having improved fire retardantproperties comprising a polyolefin and a compound selected from thegroup consisting of 1,2,3,4-tetrahalonaphthobornadienes,1,2,3,4,7,7-hexahalonaphthobornadienes,1,2,3,4-tetrahalo-7,7-dialkoxynaphthobornadienes,1,2,3,4-tetrahalo-7-one-naphthobornadienes and2,3,4-trihalo-9,10,4a,9a-tetrahydroanthracene-1-carboxylic acid whereinsaid compound is present in a concentration of 5 to 50 part by weightper 100 parts by weight polyolefin.
 2. The composition of claim 1,wherein said polyolefin comprises polypropylene.